Self-piercing riveting (SPR) is a well-known technique used in vehicle assembly as an alternative to resistance spot welding in applications or locations where welding may be difficult or even impossible to accomplish. In programmable pogo SPR, a rivet gun and a die move together, with one being substantially directly opposite the other, over opposite surfaces of two aligned sheet metal parts to a series of rivet locations. At each such location, a rivet is driven through the parts by the rivet gun, and the projecting shank or end of the driven rivet is shaped by the die. The rivet pierces or creates its own hole through the parts as it is driven. This is in contrast to other prior art riveting techniques in which the rivet is driven through a pre-drilled, pre-punched, or otherwise pre-existing hole. As a result of the SPR process, the parts are securely fastened together by the rivet's head on one side, and by the shape formed at the end of the rivet's projecting shank on the other side.
Unfortunately, this process requires the application of substantial force, typically between 30 kN and 50 kN depending on such factors as the material and thickness of the parts, to cause the rivet to properly penetrate fully through the parts. Such forces, in turn, necessitate large and stiff C-frame support structures for carrying the rivet gun and die, especially if a long reach is required. As a result, these C-frame support structures are often too heavy for use in robotic applications.
Due to these and other problems and limitations in the prior art, an improved self-piercing riveting system or method is needed.